Unchanging environmental conditions during the 'Viliafranchian" time-span in littoral basins (eastern Betics, SE Spain)

Abstract

The occurrence of littoral basins along the Mediterranean waterfront of the Eastern Betics Cordilleras (SE Spain) was a characteristic feature during the Plio-Pleistocene. Their development responds to the progressive emersion of the former marine Tortonian-Messinian basins, being common the establishment of transitional environments. In particular, the study of the different "Pliocene facies" of SE Spain in the Murcia-AIicante zone (present Lower Segura and Campo Cartagena-Mar Menor basins) reveals that their distribution is matched by the occurrence of different transitional sedimentary environments coinciding with the present location of these two basins. Initial conditions were characterized by the development of a lagoon-barrier island system along the entire basin. In the Campo Cartagena-Mar Menor zone (South) the installation of feeding extrabasinal rivers brought abaut a change from this environment to an estuarine-paludal coastal plain system whilst, in the Lower Segura zone, the environment remained unchanged. Both zones show a continuous regressive trend during their development, but no dramatic sedimentary and/or faunal changes are recorded. Faunal contents and paleomagnetic data indicate that the development of transitional environments in the basin covers the interval from the early Pliocene up to the middle Pleistocene, i.e. including the "Viliafranchian" time-span. As far as the data reported in this work are concerned, environmental conditions remained relatively constant during the studied time interval, and there is no record of relevant climatic changes in this zone of the Betics Cordilleras. Major environmental and paieogeographical changes would have been accompanied further late Pleistocene tectonic activity.